Electrochemical devices for energy storage and energy conversion such as batteries and fuel cells contain electrodes and electrolytes to transport and harvest charges. These elements are electrically conductive, ionically conductive or both. These processes may be limited either by the electrode and membrane material's inherent conductivity level or a non-optimal electrode configuration or both.
Rechargeable batteries (or electrochemical cells) contain two electrodes which are connected through an electrolyte. These components may be prepared from a variety of materials but in general the electrode-electrolyte interface often limits efficiency of charge transport. If this interface was larger and if the distance between the electrodes was smaller, the charge transport would be more efficient.
A better electrode design would therefore be influential in improving the battery function.
U.S. Pat. No. 7,828,619 discloses a method for preparing a nanostructured composite electrode through electrophoretic deposition, and electrodes prepared by such a method. A material comprising nanoparticles and carbon nanotubes having a high aspect ratio is directly deposited on the electrode and contains no polymer.
The Journal of Power Sources, 186 (2009), pages 293-298 discloses electric field assisted fabrication of membrane electrode assemblies (MEAs) for fuel cells. Electrodes are produced in which conductive particles are aligned in an ionomer polymer upon application of an electric field. Nothing is mentioned about batteries.
WO 2010/151141 discloses a method for manufacturing an electrostatic discharge device comprising a layer of conductive particles in a cross linked polymer matrix. The method involves curing of the polymer.
In contrast to a fuel cell, which will function as long as fuel and oxygen are supplied to it, a battery will be discharged upon use. Cost and environmental concerns make rechargeable batteries attractive. Other important aspects of batteries are weight and performance after a number of charge/discharge cycles. Batteries having a low weight and/or retaining a high percentage of their initial charge after a large number of charge/discharge cycles are desirable. Common battery electrodes contain carbon and binder in order to improve conductivity. However, the carbon and binder together often constitute approximately 50% of the battery electrode material thereby contributing to the weight of the electrode and eventually the battery. It would be desirable to decrease the battery electrode weight while maintaining and/or improving the battery performance.